Down draft eliminator



1957 J. w. BROWN, JR 2,776,656

DOWN DRAFT ELIMINATOR Filed March 20, 1950 III illllllHlIl llllllllllll IIIIIIIIIIMILIV JNVENTOR. Jwwv [4/ BROWN JR ATTORNEYS.

United States. Patent DOWN DRAFT ELIMINATOR John W. Brown, Jr., Lakewood, Ohio, assignor to Brown Fintube Company, Elyria, Ohio, a corporation of Ohio Application March 20, 1950, Serial No. 150,757

7 Claims. (Cl. 126-307) This invention relates to back draft preventers for use with boilers, furnaces, stoves and the like and more particularly with domestic heating equipment.

Domestic heaters, such as furnaces, hot water heaters, boilers, stoves and the like and especially those of the gas-fired type require devices to prevent downdrafts that may occur in the chimney or flue to which the furnace is connected from reaching the burner. Such devices are necessary in gas-fired furnaces to prevent sudden gusts from blowing out the gas burners or pilots and are,

required with other types of fuels to prevent discharge of products of incomplete combustion into the building in which the heater is located.

In a typical installation, the flue pipe, which conducts the line gases from the heater, leads to a T-connection in which the flue pipe constitutes the leg of the T. From this a connection leads upwardly to the chimney r flue while a short, aligned pipe leads downwardly terminating in an open end so that in the case of downdrafts in the chimney the gases present in the chimney are discharged through the open end into the building instead of being blown back through the furnace.

Installations of this sort have inherent defects. Any downdraft causes the gases in the chimney, which under some instances may contain carbon monoxide, to be discharged within the building, and, in the absence of a downdraft, a large volume of warm air from the building is constantly drawn into the opening of the back draft preventing connection and discharged up the chimney with theflue gases. This results in an important loss of heat and further, the necessity for making up the large volume of air discharged up the chimney results in infiltration of cold airinto the building and consequent drafts and unevenheating.

According to the present invention, these difliculties are eliminated by providing a construction in which the fluegases are conducted to the chimney fine from the heater through a closed flue-pipe having no communication with the interior of the building, except through the heater, while back drafts are prevented by providing a venting opening in the chimney flue leading to the exterior of the building below the point where the furnace pipe is connected to the flue. By this means, downdrafts are prevented from reaching the furnace, there is no possibility of discharging flue gases into the building and the constant withdrawal of warm air from the building, which takes place with conventional types of back draft eliminators, is prevented.

Referring to the drawings, Figure l is a diagrammatic side view illustrating the manner in which my invention may be adapted to a conventional furnace and a conventional chimney; Figure 2 is a view of the exterior of the installation of Figure 1; Figure 3 is a perspective view of a compact heating unit embodying the back draft eliminator of the present invention; Figure 4 is a side view partially in section showing the heating unit of Figure 3 installed and connected to a chimney flue;

2,776,656 Patented Jan. 8, 1957 Figure 5 is a plan view of the installation shown in Figure 4, the view being taken as indicated by the line 5-5 on Figure 4; and Figure 6 is a sectional view showing a modified form of louver that can be used with either type of installation.

Referring to Figures 1 and 2 of the drawings, reference character 10 indicates a furnace, boiler, heater or the like which may be of any ordinary construction. The furnace embodies a conventional burner 10a to which combustion air is supplied through passage 10b leading to an opening in the front of the furnace. Combustion gases from the furnace are collected and discharged into a flue pipe 11 which is connected directly to the chimney flue 12 through the inside wall thereof. It will be noted that the flue pipe 11 is continuous and devoid of openings. The path of the hot combustion gases is indicated by the wavy arrows in Figure 1.

The chimney flue 12 is shown as being constituted by ceramic liner sections disposed within a brick chimney 13 which is partially on the exterior of the building 14. The chimney may be of any conventional construction, and the top 15 of the chimney is high enough above the roof 16 of the building to secure the desired draft.

In order to prevent downdrafts which may occur in the chimney from blowing back through the furnace pipe 11 into the combustion chamber of the furnace and thence into the house, an opening 13 leading to the exterior of the building is provided in the outside wall of the chimney flue at a point below the point of connection of the furnace pipe 11 with the flue 12. Preferably the opening 18 is substantially at ground level and is provided with louvers 19 as shown to prevent animals and birds from entering the chimney and to prevent rain and snow from blowing into the opening; the area of the opening is preferably substantially equal to the area of the fine pipe 11.

By this simple arrangement, downdrafts in the chimney, instead of going back through the flue pipe 11 into the furnace, are discharged to the exterior atmosphere as indicated by the straight arrows in Figure 1. Thus, the discharge of flue gases into the building is prevented, and at the same time, only the air required by the furnace is withdrawn from the house into the chimney; there is no constant loss of large quantities of warm air as is the case with the conventional type of downdraft preventer.

In recent years, extremely compact heaters, such as shown, for example, in my copending application Serial No. 740,597, filed April 10, 1947, and now abandoned, have been developed. Heaters of this type are installed directly against an exterior wall of a building and connected to a ceramic flue built into the wall. Figures 3, 4 and 5 illustrate the manner in which the present invention may be adapted to such heaters.

As shown in these figures, the heater indicated in general at 25 comprises a sheet metal cabinet or housing 26 having a top 27 which may be at standard counter height and which may constitute a work surface in a kitchen or utility room. Within the cabinet, the heating unit 28 is disposed; a burner 28a for liquid or gaseous fuel furnishes the heat, air being supplied to the burner through passage 281; leading to an opening in the front of the cabinet, and the unit embodies appropriate heat exchange surfaces such as described in detail in my aforesaid application so that the heat derived from the fuel can be transferred to the heating medium for the building.

The products of combustion are collected in a hood 29 at the top of heating unit 23 and flow through the hood to the short, vertically extending connection 30. The hood 29 also communicates with a downwardly extending conduit 31 which is preferably vertically aligned with the upwardly extending connection 30. Conduit 31 and 3 connection30 are bothdisposed slightly to the rear of the cabinet as shown particularly in Figures 4 and 5, and conduit 31 terminates in a rearwardly extending lateral projection 32 having a louvered opening 33 at the end thereof.

As shownparticularly in Figures 4 and"5, a heater of this typemay be installed in a house. or other building,

during construction bysimply placing the cabinet in the desired location against the wall, with the? connection 30 and the downwardly extending conduit 31 at the rear of the cabinet disposed in the wall space, for example, in

the space between studs in conventional frame construction. An opening 34- in the exterior wall of the dwelling is provided to receive the lateral extension 32, the opening34-registering with the louvered opening 33.

The installation is completed byconnecting the ceramic flue 35, which constitutes the chimney, to the upwardly extending connection 30, producing an installation similar in operation to the. previously described modification. The flue gases from the heater pass upwardly through the flue 35 without any chance of escape into the building and in the event of 21 downdraft, the gases in the chimney escape through the downwardly extending conduit 31, lateral projection 32 and opening 33 to the exterior air without there being any opening into the flue to constantly withdraw warm air from the dwelling.

in some instances it may be desirable to prevent outside air from being drawn into the chimney. To accomplish this, pivoted louvers such as shown in Figure 6 may be employed. The louver assembly there shown comprises a frame 40 carrying a plurality of vanes 41 which are pivoted on rods 42. The normal position of the vanes is as shown in full lines; the vanes overlap slightly so that the lower edge of each vane engages the upper edge of the vane immediately below it, thus preventing these vanes from swinging inwardly because of air pressure. The bottom vane is prevented from swinging inwardly by a stop 43. The vanes are preferably constructed of light metal such as aluminum and are curved in cross-section as shown, for the sake of stiffness. In response to a down-draft, the vanes swing outwardly as indicated in dotted lines, permitting the gases in the chimney to be discharged to the outside of the building as before. Those skilled in the art will appreciate that louvers of this type may be employed with both of the previously described forms of the invention.

Those skilled in the art will appreciate that various changes and modifications may be made in my invention without departing from the spirit and scope thereof and that the invention may be adapted for use with heating units, furnaces, boilers, stoves and the like of types different fronrthose specifically disclosed herein. Therefore, it is to be understood that my invention is not limited to the preferred forms described in the foregoing specification. The scope of the invention is defined in the appended claims.

Iclaim:

1. In combination, a building, a heater embodying a fuel burner disposed within the building, a chimney flue inthe building, aflue pipe providing a closed conduit for Hire gasesfrom the heater to the chimney fine and constituting, the sole connection between said heater and said chimney flue, said chimney flue having an opening of cross-sectional area at least substantially as great as the cross-sectional area of said chimney flue communicating only with the atmosphere on the exterior of said building and disposed below the point of connection of said flue pipe to said chimney flue.

21 The combination according to claim 1 wherein the heater is disposed within a cabinet positioned against a wall of the building and wherein the flue pipe is disposed within the cabinet.

3. The combination according to claim 2 wherein the opening to atmosphere on the exterior of said building is provided in a downwardly extending conduit carried by said cabinet and constituting. the portion of said chimney flue below the point of connection of said chimney flue and said flue pipe.

4. in con'ihination, abuilding, a heater embodying a fuel burner disposed within said building, a chimney flue disposed on an outside wall of said building, a flue pipe leading from the heater to the chimney flue and connected to the inside wall of said chimney flue, said flue pipe being continuous and providing a closed conduit from the burner to the chimney flue and constituting the sole connection between said heater and said chimney flue, said chimney flue having a louvered opening in the outside wall thereof communicating with the atmosphere on the exterior of said building and disposed below the point of connection of said flue pipe to said chimney flue.

5. In a heating system, a building, a heater embodying a fuel burner disposed within said building, a chimney having a flue, and means for supplying combustion air for the burner from within the building, the improvement which comprises a continuous closed conduit for flue gases from the heater to the flue, and an opening from the flue directly to the exterior of said building, said opening being disposed below the point of connection of said conduit to saidflue, said opening constituting a vent for downdrafts in the flue, and said flue having imperforate walls preventing communication between said flue and the interior of said building below said point of connection.

6. The invention defined in claim 5 wherein the opening is provided with louvers and has an area substantially equal to the cross-sectional area of said conduit.

7. The invention defined in claim 5 wherein the opening is provided with hinged louvers having pivoted vanes adapted to swing outwardly and prevented from swinging inwardly whereby the discharge of chimney gases to the exterior of the building is permitted and flow of exterior airinto'the chimney is substantially prevented.

References Cited in the file of this patent UNITED STATES PATENTS 37,683 Elberg Feb. 17, 1863 539,536 McKnight May 21, 1895 679,666 Clawson July 30, 1901 1,468,165. Moore Sept. 18, 1923 1,531,884 Soderlin Mar. 31, 1925' 1,692,576 Rote Nov. 20, 1928 1,695,308 Wilt Dec. 18, 1928 2,079,804 Jones May 11, 1937 2,165,811 Peters July 11, 1939. 2,300,468 Sammin Nov. 3, 1942 FOREIGN PATENTS 646 Great Britain of 1872 207,673 Germany Mar. 8, 1909 278,630 Great Britain Oct. 13, 1928 470,772 Germany Jan. 28, 1929 OTHER REFERENCES Fuel Oil and Oil Heat, volume 8, Issue No. 4, page 56, August 1949. (Copy in Div. 19, 110447.) 

